<!-- Licensed under a BSD license. See license.html for license -->
<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes">
    <title>Three.js - PostProcessing - Custom</title>
    <style>
    html, body {
        height: 100%;
        margin: 0;
    }
    #c {
        width: 100%;
        height: 100%;
        display: block;
    }
    </style>
  </head>
  <body>
    <canvas id="c"></canvas>
  </body>
<!-- Import maps polyfill -->
<!-- Remove this when import maps will be widely supported -->
<script async src="https://unpkg.com/es-module-shims@1.3.6/dist/es-module-shims.js"></script>

<script type="importmap">
{
  "imports": {
    "three": "../../build/three.module.js",
    "three/addons/": "../../examples/jsm/"
  }
}
</script>

<script type="module">
import * as THREE from 'three';
import {EffectComposer} from 'three/addons/postprocessing/EffectComposer.js';
import {RenderPass} from 'three/addons/postprocessing/RenderPass.js';
import {ShaderPass} from 'three/addons/postprocessing/ShaderPass.js';
import {GUI} from 'three/addons/libs/lil-gui.module.min.js';

function main() {
  const canvas = document.querySelector('#c');
  const renderer = new THREE.WebGLRenderer({canvas});

  const fov = 75;
  const aspect = 2;  // the canvas default
  const near = 0.1;
  const far = 5;
  const camera = new THREE.PerspectiveCamera(fov, aspect, near, far);
  camera.position.z = 2;

  const scene = new THREE.Scene();

  {
    const color = 0xFFFFFF;
    const intensity = 2;
    const light = new THREE.DirectionalLight(color, intensity);
    light.position.set(-1, 2, 4);
    scene.add(light);
  }

  const boxWidth = 1;
  const boxHeight = 1;
  const boxDepth = 1;
  const geometry = new THREE.BoxGeometry(boxWidth, boxHeight, boxDepth);

  function makeInstance(geometry, color, x) {
    const material = new THREE.MeshPhongMaterial({color});

    const cube = new THREE.Mesh(geometry, material);
    scene.add(cube);

    cube.position.x = x;

    return cube;
  }

  const cubes = [
    makeInstance(geometry, 0x44aa88,  0),
    makeInstance(geometry, 0x8844aa, -2),
    makeInstance(geometry, 0xaa8844,  2),
  ];

  const composer = new EffectComposer(renderer);
  composer.addPass(new RenderPass(scene, camera));

  const colorShader = {
    uniforms: {
      tDiffuse: { value: null },
      color:    { value: new THREE.Color(0x88CCFF) },
    },
    vertexShader: `
      varying vec2 vUv;
      void main() {
        vUv = uv;
        gl_Position = projectionMatrix * modelViewMatrix * vec4(position, 1);
      }
    `,
    fragmentShader: `
      uniform vec3 color;
      uniform sampler2D tDiffuse;
      varying vec2 vUv;
      void main() {
        vec4 previousPassColor = texture2D(tDiffuse, vUv);
        gl_FragColor = vec4(
            previousPassColor.rgb * color,
            previousPassColor.a);
      }
    `,
  };

  const colorPass = new ShaderPass(colorShader);
  colorPass.renderToScreen = true;
  composer.addPass(colorPass);

  function resizeRendererToDisplaySize(renderer) {
    const canvas = renderer.domElement;
    const width = canvas.clientWidth;
    const height = canvas.clientHeight;
    const needResize = canvas.width !== width || canvas.height !== height;
    if (needResize) {
      renderer.setSize(width, height, false);
    }
    return needResize;
  }

  const gui = new GUI();
  gui.add(colorPass.uniforms.color.value, 'r', 0, 4).name('red');
  gui.add(colorPass.uniforms.color.value, 'g', 0, 4).name('green');
  gui.add(colorPass.uniforms.color.value, 'b', 0, 4).name('blue');

  let then = 0;
  function render(now) {
    now *= 0.001;  // convert to seconds
    const deltaTime = now - then;
    then = now;

    if (resizeRendererToDisplaySize(renderer)) {
      const canvas = renderer.domElement;
      camera.aspect = canvas.clientWidth / canvas.clientHeight;
      camera.updateProjectionMatrix();
      composer.setSize(canvas.width, canvas.height);
    }

    cubes.forEach((cube, ndx) => {
      const speed = 1 + ndx * .1;
      const rot = now * speed;
      cube.rotation.x = rot;
      cube.rotation.y = rot;
    });

    composer.render(deltaTime);

    requestAnimationFrame(render);
  }

  requestAnimationFrame(render);
}

main();
</script>
</html>

